The present invention relates to an electronic musical instrument and more particularly to a key scaling apparatus for use in an electronic musical instrument which modifies the characteristic of a tone in accordance with the pitch or key number.
In the art of electronic musical instruments, the technology of key scaling for controlling the characteristic of a tone to depend on the key number was known. Some prior art apparatus employs a memory in the form of ROM storing key scaling data which are not programmable by a user. In operation, both a tone number selected by a timbre select switch and the key number input from a play (performance) input device such as a keyboard is used to specify a key scaling data item and read it from the memory for the control of the tone to be generated. An example is disclosed in the Japanese patent laid open (Kokai) No. 61-172,192. This arrangement is unsatisfactory not only because it requires a large amount of storage for key scaling but also because it inhibits the user from gaining access to desirable scaling data.
In another prior art, a key number which is the center of the key scaling is freely selected by the user and an envelope level sensitivity curve extending from the center of key scaling is user-selectable from a plurality of different curves which are preset in the system (see FIG. 6). In operation, the key number input from a keyboard specifies a point along the selected envelope level sensitivity curve so that the envelope sensitivity data at that point is used to modify the envelope level. Such technology is incorporated in a music synthesizer known as DX7. While this arrangement provides an environment in which the user can select the characteristic of the key scaling, it limits satisfactory key scaling response to those regions around the central key number.